1. Field of the Invention
The present invention relates to a disk player, more precisely relates to a disk player, which is capable of playing data recorded on a disk by the CLV (Constant Linear Velocity) recording form.
2. Description of Background Art
Generally, in conventional disk players, e.g., CD-ROMs, CD-Is, the rotational speed of a disk is continuously controlled so as to maintain playing linear velocity, which is the tracing length of an optical pick-up of the disk player per a predetermined unit time. Thus, a motor for driving the disk is controlled on the basis of the servo control method.
The conventional disk player comprises:
a motor for rotating a disk; PA1 an optical pick-up for reading data recorded on the disk, the optical pick-up being capable of moving in the radial direction with respect to the disk driven by the motor and outputting the data read as data signals; PA1 a first clock section for generating master clock signals, the first clock section being capable of changing the frequency of the master clock signals by two stages; PA1 a second clock section for extracting synchronizing signals from the data signals and generating second clock signals whose frequency is equal to the frequency of the synchronizing signals; PA1 a comparing section for comparing mutual frequency and phase of the master clock signals and the second signals and generating deviation signals whose voltage level corresponds to the differences of the frequency and the phrase thereof; and PA1 a drive section for sending drive signals, whose voltage level changes according to voltage changes of the deviation signals, to the motor, whereby the drive section controls the motor so as to synchronize the frequency and the phase of tile second clock signals with those of the master clock signals. PA1 an optical pick-up for reading data recorded on the disk, the optical pick-up being capable of moving in the radial direction with respect to the disk driven by the motor and outputting the data read as data signals; PA1 a first clock section for generating master clock signals, the first clock section being capable of changing the frequency of the master clock signals by multiple stages; PA1 said first clock section including a voltage controlled oscillator for generating the master clock signals, an oscillating circuit for generating standard clock signals having predetermined frequency, a first divider circuit for dividing the standard clock signals and generating first divided signals, a second divider circuit for dividing the master clock signals and generating second divided signals, and a phase comparing circuit for comparing the phase of the first divided signals and the second divided signals and generating phase-deviation signals corresponding to the phase deviation thereof and a processing section for generating setting signals, which respectively define the dividing ratio of said first divider circuit and said second divider circuit; PA1 a second clock section for extracting synchronizing signals from the data signals and generating second clock signals whose frequency is equal to the frequency of the synchronizing signals; PA1 a comparing section for comparing mutual frequency and phase of the master clock signals and the second signals and generating deviation signals whose voltage level corresponds to the differences of the frequency and the phrase thereof; and PA1 a drive section for sending drive signals, whose voltage level changes according to voltage changes of the deviation signals, to the motor, whereby the drive section controls the motor so as to synchronize the frequency and the phase of the second clock signals with those of the master clock signals.
In the above described conventional disk player, if the frequency of the second clock signals is higher than that of the master clock signals, the voltage level of the deviation signals from the comparing section rises, so that the voltage level of the drive signals from the drive section to the motor falls. Therefore, the rotational speed of the motor is braked, and the frequency of the second clock signals is lowered to that of the master clock signals. On the other hand, if the frequency of the second clock signals is lower than that of the master clock signals, the voltage level of the deviation signals from the comparing section falls, so that the voltage level of the drive signals from the drive section to the motor rises. Therefore, the rotational speed of the motor is accelerated and the frequency of the second clock signals is increased to that of the master clock signals. Since the rotational speed of the disk is controlled on the basis of the above described feed back control method, the playing linear velocity can be maintained at a predetermined velocity.
Moreover, in the conventional disk player, sub codes, data bits, etc. in the data signals are sampled on the basis of the master clock signals or the second clock signals. When they are sampled, firstly the first clock signals are controlled so as to make the playing linear velocity at standard velocity. Afterwards, if the sampling is precisely executed, the playing linear velocity is changed to a higher velocity so as to accelerate the reading speed of the optical pick-up. If sampling errors often occur after the the first clock signals have been switched to higher, the first clock signals are changed to the standard again. The data recorded are read by reciprocally executing the above described control.
However, the conventional disk player has the following disadvantages.
Generally, when the playing linear velocity is higher, sampling errors are likely to occur, so that the number of re-try is increased. Therefore, in case of a lower playing linear velocity with no sampling error, the reading time can be shorter than the case of the higher playing linear velocity with many sampling errors. But the conventional disk players has only two playing linear velocities, that is, the standard velocity and the higher velocity. No intermediate velocity between the standard velocity and the higher velocity can be selected.
In addition, case of playing soiled or damaged disks, the number of the re-try is fairly increased, so that the playing linear velocity is substantially fixed to the standard velocity and the reading time is not improved.